<template>
<!--當列表沒有資料時,不需顯示-->
     <div class="todo-footer" v-show='total'> 
        <label>
          <input type="checkbox" v-model="isAll"/>
        </label>
        <span>
          <span>已完成{{doneTotal}}</span> / 全部 {{total}}
        </span>
        <button class="btn btn-danger" @click="clearAll">清除已完成任务</button>
      </div>
</template>

<script>
	export default {
		name:'MyFooter',
		props:['todos','checkAllTodo','clearAllTodo'],
		computed:{
			total(){
				return this.todos.length
			},
			doneTotal(){
			return this.todos.reduce((pre,todo)=> pre +(todo.done ? 1:0),0 )
			// reduce 計算統計 按照數組的長度調用 pre:上一次調用的返回值
			},
			isAll:{
			get(){
			return this.doneTotal === this.total && this.total>0 //當列表沒有資料時,不需勾選
			},
			set(value){
				this.checkAllTodo(value)  //返回布爾值
			}
			},
		},
		methods:{
			clearAll(){
			this.clearAllTodo()
			}
		}
	}
</script>

<style scoped>
	/*footer*/
	.todo-footer {
		height: 40px;
		line-height: 40px;
		padding-left: 6px;
		margin-top: 5px;
	}

	.todo-footer label {
		display: inline-block;
		margin-right: 20px;
		cursor: pointer;
	}

	.todo-footer label input {
		position: relative;
		top: -1px;
		vertical-align: middle;
		margin-right: 5px;
	}

	.todo-footer button {
		float: right;
		margin-top: 5px;
	}
</style>